(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of an improved buried contact trench in the fabrication of integrated circuits.
(2) Description of the Prior Art
A typical buried contact is formed by depositing a doped layer of polysilicon over and on the planned buried contact regions and heating the structure. The buried contact regions are doped by outdiffusion of dopants from the doped polysilicon layer into the silicon substrate. The doped polysilicon layer is allowed to remain on the buried contact regions as their contacts. If there is misalignment of the mask during etching of the polysilicon, a portion of the semiconductor substrate within the buried contact area will be exposed. During polysilicon overetching, a buried contact trench will be etched. The buried contact is formed to connect the polysilicon and the substrate. If the buried contact trench is so deep as to be a barrier to the current flow from the polysilicon to the substrate, or the reverse, the integrated circuit will not function correctly.
U.S. Pat. No. 5,350,712 to Shibata teaches the use of an additional metal width around a metal line to overcome mask misalignment problems causing etching of the semiconductor substrate.